Abstract

BackgroundThe first-line treatment for symptomatic Morton’s neuroma in our hospital is a perineural ultrasound-guided injection of corticosteroid and local anaesthetic (USI). The NHS has recently implemented 18-week referral-to-treatment targets. When GPs specifically suggest a diagnosis of Morton’s neuroma there are two referral pathways in our hospital: direct referral to radiology for USI (limited slots) or referral to the specialist foot and ankle clinic. Patients with less specific referral letters are also evaluated in clinic and referred for USI as appropriate. MethodsA retrospective audit was performed reviewing referral letters from general practitioners (GPs) in 2005–2006.Acomparisonwasmadebetween the referral pathways for time-to-treatment (TTT), accuracy of GP diagnosis, and cost implications. ResultsIn the directly referred group, the median TTT was 99 days, compared to 206 days for patients who went via a foot and ankle clinic (P 0.001). Of 57 patients with a GP diagnosis of Morton’s neuroma, 40 (70%) had the diagnosis confirmed on USI compared to 44 of 64 (69%) patients referred by a foot and ankle surgeon, showing no significant difference between the groups (P = 0.87). ConclusionFor patients with features highly suggestive of a Morton’s neuroma, direct referral from primary care for USI had a similar accuracy to referral from a specialist hospital clinic and the time-to treatment was significantly shorter. Themean waiting time of this group was within the 18-week government target without any changes to our current radiology protocols.

Keywords

Introduction

Morton’s neuroma is a painful condition of the foot,
characterised by neural degeneration and perineural
fibrosis, most commonly seen between the third and
fourth or the second and third metatarsals.[1] Itwas first
described by Durlacher in 1845.[2] Thomas Morton, in
1876, described the syndrome as ‘a peculiar painful
affection of the fourth metatarsophalangeal articulation’.
[3]

The exact pathogenesis of Morton’s neuroma is
uncertain, but the currently accepted theory is that it
is caused by repetitive trauma of the plantar nerve at
the edge of the metatarsal ligament which leads to
perineural fibrosis.[1] Nissen suggested that the pathology
was a vascular phenomenon leading to neurofibrosis,[4]
whereas Bossley and Cairney suggested that swelling of
the intermetatarsal bursa compressed the nerve, resulting
in a neuroma.[5] Debate rages as to the significance
of the swelling of an interdigital nerve and its relationship,
or not, to symptoms characteristic of a Morton’s
neuroma.

Previous small studies have estimated the prevalence
of Morton’s neuroma to be around 30%.[6,7] It
most commonly presents with pain in the forefoot,
radiating to the two involved toes, with pain aggravated
by wearing pointed and high-heeled shoes and
relieved by taking the shoes off and massaging the foot.
Patients often complain of feeling as if they are walking
on a stone in their shoe. Not all patients have such
specific symptoms. A positive web space compression
test, performed by squeezing together the metatarsal
heads with one hand and with the other hand compressing
the involved web space between thumb and
finger and producing severe pain, is highly suggestive
of a Morton’s neuroma.[8]

Diagnosis in most centres can be made using either
ultrasound,[9–12] or magnetic resonance imaging (MRI),[13,14]
although some studies show that clinical evaluation is
as accurate as radiological diagnosis.14Morton’s neuroma
can be treated conservatively using shoe modifications,
or if this fails to improve symptoms then ultrasoundguided injection using a combination of steroids and
local anaesthetic can be used to relieve symptoms.
Other surgical options include neurolysis, percutaneous
electrocoagulation, cryogenic denervation of the intermetatarsal
neuroma or surgical decompression.[15]

In our primary care trust (PCT), general practitioners
(GPs) have direct access to orthotic services
and so patients with mild symptoms will usually be
referred there first. At the Nuffield Orthopaedic Centre,
a secondary and tertiary elective orthopaedic hospital,
the first-line treatment for patients referred with symptomatic
Morton’s neuroma is an ultrasound (US)-
guided evaluation, and injection of depo-medrone
and bupivacaine. Failure of successive injections to
resolve symptoms leads to the offer of surgical treatment.

This retrospective audit was undertaken to improve
waiting time for patients from referral to ultrasoundguided
injection (USI). There are two referral pathways
in our hospital:

A direct referral to US injection upon receipt of a
GP referral letter suggesting a specific diagnosis of
Morton’s neuroma, for which we have a limited
number of slots

B assessment in a foot and ankle clinic referral to
USI as appropriate, for all remaining referrals.

The aims of this audit were firstly to investigate the
difference in time to treatment (TTT) between the two
referral patterns, and secondly to ascertain the accuracy
with which GPs were able to diagnose Morton’s
neuroma. A further aim was to consider the financial
implications of treating patients using these two
referral patterns.

Methods

Patients were included in the audit if they were
referred by GPs between January 2005 and December
2006 to the Nuffield Orthopaedic Centre Foot and
Ankle team, with a specific diagnosis of Morton’s neuroma in their referral letter. Data were collected
from patients’ clinical notes, referral letters, and radiology
reports, and, using these, we excluded patients
with recurrent Morton’s neuroma.

Time to treatment

The assignment into one of two groups was recorded:
direct referral to US for injection (group A), or
attendance at the foot and ankle clinic for assessment,
with referral to ultrasound if appropriate (group B: see Figure 1).

For group A, a forwarding letter had been sent to the
radiology department with a copy of the GP referral
letter, and a US appointment was made. For group B,
a routine outpatient appointment was made to see a
member of the foot and ankle team. Patients were
assessed in clinic and referred on to USI, as appropriate,
by means of a dictated clinic letter. We compared
their TTT.

The USIs were performed by three experienced
consultant musculoskeletal radiologists using a 12 MHz
linear transducer in the sagittal and axial planes. US
was performed on the dorsum and sole of the foot, and
feet were injected from the dorsal side using a combination
of 40 mg depomedrone and 5–10 mg bupivacaine.

Accuracy of diagnosis

In order to determine accuracy of GP diagnosis of
Morton’s neuroma, we compared the success rate of
diagnosis within groups A and B to a further group (C: see Figure 1). Group C were patients referred by a foot
and ankle consultant to USI, querying a Morton’s
neuroma during the same period. These patients did
not have a GP diagnosis ofMorton’s neuroma in their
referral letter but symptoms were described as ‘metatarsalgia’
or ‘forefoot pain’ or some other condition.

Cost evaluation

Costs of an outpatient appointment were obtained
from the trust.

Statistical methods

Data for TTT were seen to be non-parametric by visual
assessment of frequency histograms, and therefore a
Mann–Whitney U test was used to compare groups.
For the comparison of accuracy in diagnosis, a 2 test
was used and a two-tailed P value calculated. Statistical
analyses were performed using SPSS version 17.0
(Illinois, USA).

Results

There were 29 patients in group A, 27 female and two
male, with a median age of 57 years (range 27–87
years). There were 28 patients in group B, 19 female
and nine male, with a median age of 59 years (range
31–89 years). In group C there were 64 patients, 53 female, 11 male, with a median age of 53 years (range
27–87 years).

Figure 1: Referral pathways for treatment of Morton’s neuroma

For all 28 patients in group B, the foot and ankle
surgeon agreed with the GP’s diagnosis of Morton’s
neuroma; hence they all proceeded on to radiology for
a US.

Time to treatment

The TTT for the 29 patients in group A was compared
to the 28 patients in group B. The median TTT in
group A was 99 days (interquartile range (IQR) 23
days), and was significantly shorter than that for group
B, 206 days (IQR 51 days; P < 0.001).

Accuracy of diagnosis

For those 57 patients in whom the GP had suggested a
diagnosis of a Morton’s neuroma, 40 (70%) had
confirmed Morton’s neuroma on US and proceeded
to injection. The other US findings are summarised in Table 1.

Of the 64 patients in group C, 44 (69%) had a
confirmed diagnosis of Morton’s neuroma. There was
no statistically significant difference between the two
groups (χ2 = 0.029, P = 0.87). No patient had their
diagnosis subsequently refuted, and the diagnosis following
US imaging was found to be appropriate in
each case.

Cost evaluation

The cost of an outpatient appointment was £175. By
preventing 29 outpatients appointments the saving to
the trust was estimated to be £5075.

Discussion

Time to treatment was significantly shortened by more
than a half with direct referral to USI from primary
care compared to referral via a specialist clinic. There
was no significant difference in accuracy of diagnosis
ofMorton’s neuroma between GPs and foot and ankle
surgeons. In addition, there was a saving of 29 outpatient
appointments, amounting to approximately
£5075.

There are a number of limitations in this study. The
first is that our comparison of GP diagnostic accuracy
compared to that of a foot and ankle surgeon was
conducted with different patient cohorts. Patients
presenting to a GP may not have a clear-cut diagnosis
of a Morton’s neuroma and it is appropriate that this
group of patients should be seen by a foot and ankle
team member. However, it is important to note that
the alternative diagnoses in group A (see Table 1)
would have warranted a US, even if these patients
had been seen first in a specialist clinic. Secondly, the
success rate for GPs correctly diagnosing Morton’s
neuroma was achieved with them being blinded to the
fact that this audit was being conducted.

TheNHSImprovement Plan (June 2004) set out the
following aim: ‘By 2008 no one willwait longer than 18
weeks from GP referral to hospital treatment’. The
subsequent guidance document was released in May
2006,16 leading to added pressures on an already busy
foot and ankle service.

Waiting times have dramatically dropped in our
hospital for all conditions since this audit, but the
principle of saving costs and reducing delay is important
in our practice. Experienced musculoskeletal radiologists
screen patients for alternative diagnoses because,
although asymptomatic patients may be shown to have a
‘neuroma’ on ultrasound, this is not enough to make
the diagnosis. Radiologists can also visualise the forefoot
for other diagnoses such as mechanical overload,
synovitis or instability of the metatarsophalangeal joints
or tendon sheaths, seronegative arthritides, tumours,
bursae and stress fractures or reactions of metatarsals.

The literature describes that ultrasound, computerised
tomography (CT) and MR imaging have all previously
been used in the investigation of patients
whose clinical findings are suggestive of Morton’s
neuroma.[9,13,14,17] Ultrasound has been found to be
specific and sensitive but operator dependent,[9,10,12,14]
with some studies quoting prospective sensitivity of
up to 98%, and retrospective sensitivity of up to
100%.[11,12] We are fortunate to have highly experienced
specialist interventional musculoskeletal radiologists
in our hospital.

Morton’s neuroma and its treatment remains a
controversial topic of foot and ankle surgery today. At
our hospital, we have an established primary treatment using ultrasound with steroid and local anaesthetic injection.
A recent Cochrane review in 2004 concluded that
there were no well-designed randomised controlled
trials to evaluate the outcome of various treatments
for Morton’s neuroma.[18] The published literature
shows varying rates of success from injection; two
recent papers have success rates of 69% and 82%,
respectively.[19,20] Research has also shown alcohol injection
to be a treatment of similar efficacy,[21,22] but this
requires multiple injections, with over four injections
per patient in one study.[21] This supports selection of
our primary treatment, with surgical excision reserved
for those patients in whom primary treatment is
unsuccessful.

As a result of this audit, a direct referral to USI for
suspected cases of Morton’s neuroma is being negotiated
between the PCT and our hospital. The financial
implications of this audit were a saving of [29] outpatient
appointments in two years; with the implementation
of this protocol to all patients for whomthe
GP suggested in their referral letter a diagnosis of
Morton’s neuroma, we would have saved 57 outpatient
appointments at cost saving of just under
£10 000.

In the UK, there are an increasing number of
specialist interventional musculoskeletal radiologists.
For areas where the local policy of Morton’s neuroma
treatment is USI, we would advocate consideration or
a trial of direct referral. Locally, we anticipate studying
if there is an increase in numbers referred directly to
USI, and if the implementation of direct access has any
effect on the accuracy of GP diagnosis of Morton’s
neuroma or leads to over-referral due to ease of access.

Sharp RJ, Wade CM, Hennessy MS and Saxby TS. The role of MRI and ultrasound imaging in Morton’s neuroma and the effect of size of lesion on symptoms. The Journal of Bone and Joint Surgery 2003;85(7):999–1005.